Microsoft Automatic Private IP Addressing (APIPA) -

Have you ever get PC automatically change to 169.x.x.x?

If yes, maybe it's because of the APIPA (Microsoft Automatic Private IP Addressing).
When the DHCP server was crash and when the client don't get any IP address from the server, APIPA assign a random IP address from the range through to the host.

Disable APIPA

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces subkey. 

Select the string that identifies your adapter, and create a new DWORD Value.
Name the entry IPAutoconfigurationEnabled, and set the value to 0.
If you have multiple adapters, repeat the process for each adapter under the Interfaces subkey